Medium for use in making camera copy and method of preparing same



Aug. 15, 1944. M. D. MCINTOSH MEDIUM FOR USE IN MAKING CAMERA COPIES ANDMETHOD OF PREPARING SAME Filed Aug. 15, 1942 INVENTOR. MAURICE D.MINTOSH 4% AT ToRNEYs Patented Au '-.j15,"1944 J UNITED mg MEDIUM FORuse in MAKING omens COPY AND METHOD SAME OF PREPARING Maurice D.-McIntosh, Cleveland Heights, Ohio,

asaignor to Louis S Sanders, Shaker Heights,

application august is, an, Serial No. assess '8 Claims.

This invention relates, as indicated, to a medium for use in makingcamera copy," method of preparing the same. In my ReissuePatent No.20,503, I have deand to a scribed a drawing paper having a plurality ofnormally invisible patterns, one of the patterns being developable by adeveloper solution capable of developing said pattern only and both ofthe patterns being developable by a, developer solution capable ofdeveloping both of the patterns collectively. In the specific exampledescribed in said patent, one of the p'attems consists of a plurality ofgeometrically arranged dots located in equally-spaced diagonal rows insuch a manner that the dots in one of the rows align with adjacent dotsin the other rows to form diagonal rows extending transversely of thefirst-named rows. The other pattern consists 01 diagonal lines extendinglongitudinally of and in registry with the respective diagonal rows ofdots.

While this method of forming the patterns is, in general, satisfactory,its value depends to a great extent on securing perfect registry orproper relative location between the dots and lines, a condition whichis often exceedingly difficult to obtain by the ordinary method orforming the patterns, that is, printing the patterns I by means ofplates.

I have discovered, however, that I can secure perfect registry or properrelativelocation between different patterns by the simple expedient ofsuperimposing one pattern in the form of small dots, over another,in theform of larger dots, both patterns being formed in such a manner thatregistry between two diflerent printing plates, as described in myaforesaid reissue pateat, is not necessary. In the description whichfollows, the first or superimposed pattern will sometimes be referred toas the-flrst tone, and the other pattern, consisting of the small andlarge dots, will be referred to as the second tone.

The invention can probably best be understood by reference to theaccompanying drawing, wherein,

Fig. 1 is a fragmentary perspective view, illus-.

trating the first stage in the manufacture of the medium of the presentinvention;

Fig. 2 is a fragmentary perspective view of a reverse dot printing platewhich is used in making the medium;

' Fig. 3 is a view similar to Fig. 1, but showing the reverse dotprinting plate of Fig. 2 in position to transfer the varnish thereon tothe gelatin-coated surface or the sheet of Fig. 1;

Fig. 4 is a cross-sectional view of the assembled elements of Fig. 3; 4

Fig. 5 is a view similar printing plate removed;

Fig. 6 is a fragmentary plan view, on an enlarged scale, of the sheetshown in Fig.5;

Fig. 'l is aview similar to Fig. 6, but showing, in dotted lines, theextent of penetration of the lead acetate solution into the gelatincoating;

Fig. 8 is a view similar to Fig. '7, but showing, in dash-dot lines theextent of or area of the to Fig. 4, but with the mercurous nitrate dots;

, like.

Fig. 9 is a view similar to Fig. 8, but showing the appearance of thesheet after removal of the original varnish imprint and afterdevelopment of the smaller dots, and

Fig. 10 is a view similar to the development of both dots.

Referring more particularly to the drawing, and especially to Fig. 1, Irepresents a base sheet, which may be of paper or a synthetic plasticfilm, such as cellulose acetate, ethyl cellulose, or the Barytacoated'paper, as used for thebase of photographic print paper is alsosuitable for this purpose.

To this base sheet is applied a thin coating 2 of plain gelatin of athickness of from .001" to .002". This may be applied to the material byusing an aqueous solution containing 10% by weight of plain gelatin, thesolution being applied warm, using a whirl coating or roll coatingmachine, or any other means whereby a uniform gelatin coating of-therequisite thickness is obtained.

Instead of coating a base sheet with gelatin, a gelatin-coated sheet,available in the market. such for example, as imbibition paper furnishedby Eastman Kodak Company, may be used.

A printing plate 3 is then prepared having a multiplicity of openings 4therein, which are shown as circular, but which may be square or anyother desired shape, these openings being spaced from each other in amanner similar to the spacing of dots in an ordinary Ben Day pattern.Such openings, in actual practice, are extremely small and spaced veryclosely together, but the size and spacing are greatly enlarged in thepresent drawing, for purposes of clarity. A film I of any waterresistant printing varnish or ink is then applied to the plate 3 in sucha manner that the varnish or ink covers the entire suri lace 4of theplate, with the exception of the open- The film 5 is then transferreddirectly to the Fig. 9, but showing gelatin film 2 of the sheet I, inthe manner shown in Figs. 3 and 4, that is by ap lying the plate 3,varnished side down, to the film 2 oi the sheet. Instead of using a fiatprinting plate, a cylin-v drical or rubber type of printing devicehaving openings therein may be used to apply a film of varnish or ink tothe film 2.

The plate 3 is then removed. leaving a, gelatincoated sheet, upon whichis superimposed a varnish imprint, containing circular openings 2forming a dot pattern, and through which the gelatin coating is exposed.v

The varnish print is then permitted to dry, whereby it becomeswaterproof and impermeable to those chemicals, with the exceptionofvarnish solvents, which will presently be described.

The sheet is next immersed in a 20% aqueous solution of normal leadacetate, as a result of which the lead acetate solution enters theopenings 2' in the varnish imprint, enters the gelatin coating anddiffuses radially into the gelatin coating under the varnish, the extentof radial penetration of the lead acetate solution into the gelatinbeing indicated by the dotted circles in Fig. 7. The diffusion is slowand proceeds uniformly in all directions. The extent of area panetratedby the lead acetate solution will be determined by the length of timethe lead acetate solution is allowed access to the gelatin in theopenings 2', and this, in turn, will predetermine the size of the dot ordot units comprising the second tone, to which reference has been made.It is apparent therefore that by controlling the time of immersion ofthe sheet in the lead acetate solution, any desired tone value for thesecond tone" in the finished medium can be obtained.

Immediately upon removal of the sheet from the lead acetate solution,the surface thereof is dried by blotting or running the sheet betweensoft rubber rollers, and the sheet is permitted to become thoroughlydry, after which it is immersed in the following solution:

Parts Water 100 Nitric acid (specific gravity 1.42) 9 Mercurous nitrateAs a result of this second immersion, the mercurous nitrate solutionalso enters the openings 2' in the varnish imprint, enters the gelatinc0at ing and difluses radially into the gelatin coating under thevarnish, the extent of radial penetration of the mercurous nitratesolution into the gelatin coating being indicated by the dot-dashcircles in Fig. 8. The diffusion is slow and proceeds uniformly in alldirections.

Here again, the time of immersion will determine the size of thesuperimposed dots of mercurous nitrate and accordingly, the value of the"first tone, to which reference has been made.

The superimposed dots must necessarily be smaller than the underlyingsecond tone dots in order to secure a useful difference in the finaltone values.

It may also be pointed out that any desired relationship between thefirst tone" dots and the already established second tone dots can befixed or determined at this point by control of the duration ofimmersion.

After the sheet is removed from the mercurous nitrate solution, it isimmediately immersed in a 5% aqueous solution of sodium chloride andpermitted to remain therein slightly in excess of the immersion periodin the mercurous nitrate I solution. The mercurous nitrate in thegelatin in those areas penetrated by the sodium chloride solution.Precipitation of all of the lead acetate to lead chloride may or maynotoccur, but at this point it is unnecessary to fix the lead a-cetate inposition, since a subsequent treatment which will presently bedescribed, will effectively accomplish this.

After removal of the sheet from the sodium chloride solution, it isagain blotted or run through rollers to remove all surface excess of thesolution, and is then permitted to become thoroughly dry. I

After the sheet has become thoroughly dry, it is sponged with a solventfor the original varnish imprintin order to remove the varnish. For,

this purpose, anyone of a number of organic solvents may be employed,but the solvent must be one that will not be a solvent for lead acetate,since some lead acetate may, as previously stated, iemain in the gelatinunchanged by the sodium chloride treatment. The mercurous chloride andthe lead chloride will not be soluble in any practical varnish solvent.Carbon tetrachloride, benzol, toluol, xylol, butyl alcohol and amylalcohol are examples of suitable solvents for varnish.

Ethylene glycol monomethyl ether is particularly suitable since it isnontoxic and its vapors are not easily combustible. The varnish iseasily wiped clean from the gelatin surface by using soft cotton flannelsaturated with the solvent. The sheet, as it appears after removal ofthe varnish imprint, is shown in Fig. 9.

After removal of the varnish, the sheet is immersed for two minutes in a10% aqueous solution of sodium sulphate (anhydrous), which changes boththe lead acetate and lead chloride to the more insoluble lead sulphate,which becomes permanently fixed within the gelatin.

Thus any lead acetate which was not converted to lead chloride by thesodium chloride treatment is converted into lead sulphate. The sodiumsulphate solution apparently has no effect on the mercurous chloride.

The medium now exists as a plain l in film on either a paperor'transparent plastic base. Within the gelatin surface are two white(actinic color) insoluble chemical dot patterns, the one a series ofuniformly spaced dots of lead sulphate of a predetermined uniform size,and the other, a. series of dots of mercurous chloride exactlysuperimposed upon the lead sulphate dots and of a smaller uniform size,the superimposition of one series of dots upon another resulting in anexact registration or proper relative location between the dots.

The medium thus prepared is the medium of the present invention for usein making camera copy. 1

After a suitable drawing, as for example, an ink line drawing has beenmade upon the medium, one or both of the patterns may be developed indesired areas as a shading or accompaniment of such line drawing.

In order to develop the first tone," a chemical developer composed of100 parts of water and 1.3 parts of thiourea is applied to the sheet, asby means of a brush, thereby changing the mercurous chloride dots to ablack or brown nonactinic color and producing a Ben Day tone of onevalue, as shown in Fig. 9. In order to defilm will, through doubledecomposition, be velop the second tone, a chemical developer The leadacetate solution composed of 100 parts of water and 4 parts of sodiumsulphide is applied to the sheet, as by means of a brush, therebychanging both the mercurous chloride and lead sulphate dots to a blackor brown color and producing a Ben Day tone of a greater value, as shownin Fig. 10.

Instead of using lead sulphate for forming the pattern for the secondtone, other actinic colored insoluble chemical compounds which willreact with a solution of a soluble sulphide to produce a non-actiniccolored compound may be used. Among these are cobaltous tungstate,nickelous phosphate, cupric tungstate, ferric phosphate and thalliumtungstate.

I claim:

1. In a method of preparing a medium for use in making camera copy, thesteps which consist in impregnating a surface with achemically-developable pattern comprising spaced dots, and thenimpregnating said surface with a chemically-developable patterncomprising spaced dots smaller than said first-named dots, saidsecond-named dots being substantially entirely superimposed upon saidfirst-named dots.

2. In a method of preparing a medium for use in making camera copy, thesteps which consist in impregnating a surface with chemicals, whosereaction produces a pattern consisting of spaced dots of lead sulphate,impregnating said surface with chemicals whose reaction produces apattern consisting of spaced dots of mercurous chloride, saidsecond-named dots being smaller than said first-named dots andsubstantially entirely superimposed upcn the latter.

3. In a method of preparing a medium for use in making camera copy, thesteps which consist in applying to a gelatin-coated base sheet animprint of a water-proof material having uniformly spaced openingstherein, and introducing into said openings, in succession, a pluralityof chemicals, the reaction of which produces chemically-developable dotsin said gelatin, which are exposed, in part at least, through saidopenings.

4. In a method of reparing a medium for use in making camera copy, thesteps which consist in applying to a gelatin-coated base sheet a film ofvarnish having uniformly spaced openings, therein, immersing said sheetin a lead acetate solution whereby to impregnate the gelain and adjacentsaid openings with said acetate solution, drying said sheet, and thenimmersing said sheet in a mercurous nitrate solution, whereby toimpregnate the gelatin in said openings with said mercurous nitratesolution.

5. In a method of preparing a medium for use in making camera copy, thesteps which consist in applying to a gelatin-coated base sheet a film ofvarnish having uniformly-spaced openings therein, immersing said sheetin a lead acetate solution whereby to impregnate the gelatine belowsaidopenings with said acetate and cause it to diffuse in said gelatinradially of said openings, drying said sheet, immersing said sheet in amercurous nitrate solution, whereby to cause said nitrate to impregnatethe gelatin below said openings and to diffuse radially of the latter,but not to the same extent as the acetate, then immersing the sheet in asodium chloride solution to change the mercurous nitrate to mercurouschloride and the lead acetate to lead chloride, again drying the sheet,removing the varnish film, and then immersing the sheet in a sodiumsulphate solution to change the lead chloride to lead sulphate.

6. A medium for use in preparing camera copy,

said medium consisting of a surface having chemically-developablepatterns thereon, one of said patterns consisting of uniformly spaceddots of one substance, and the other of said patterns consisting ofuniformly spaced dots of another substance smaller than said first-nameddots and superimposed upon the latter.

7. A medium for use in preparing camera copy, said medium consisting ofa surface having chemically-developable patterns thereon, one of saidpatterns consisting of uniformly spaced dots, and the other of saidpatterns consisting of uniformly spaced dots smaller than saidfirstnamed dots and superimposed upon the latter, said second-named dotsbeing developable to visibility by means of a chemical, and both of saiddots being developable by means of a chemical different than that usedfor developing said second-named dots to produce a tone of greatervalue.

8. A medium for use in preparing camera copy, said medium consisting ofa surface having chemically-developable patterns thereon, one of saidpatterns consisting of uniformly spaced dots of lead sulphate, and theother of said patterns consisting of uniformly spaced dots of mercurouschloride superimposed upon and of a smaller size than said first-nameddots.

MAURICE D. McINTOSH.

